The long term objective of this proposal is to elucidate the mechanisms for regulation of brain adenylate cyclase by calmodulin (CaM) and the cAMP dependent protein kinase. Recent data from this laboratory using azido[125I]CaM and partially purified adenylate cyclase have implicated a 150,000 dalton polypeptide as the catalytic subunit of the CaM sensitive adenylate cyclase from bovine cerebral cortex. This polypeptide has been isolated in quantity by preparative SDS gel electrophoresis and shown to elicit polyclonal anti-cyclase antibodies with rabbits. We have also discovered that the catalytic subunit of protein kinase inhibits the activity of the CaM sensitive adenylate cyclase in the presence of ATP. It is our working hypothesis that direct phosphorylation of this adenylate cyclase may inhibit enzyme activity. The specific aims of this project include further purification of the CaM sensitive adenylate cyclase, preparation of monoclonal and polyclonal antibodies against specific polypeptides in the preparation, and elucidation of the quaternary structure of the enzyme complex. In addition, the significance of protein kinase inhibition of the enzyme will be evaluated.